Technical Abstract:
Fusarium graminearum infection contaminates wheat and barley grain with the potent trichothecene mycotoxin deoxynivalenol (DON). Trichothecene mycotoxins are known to target cytosolic ribosomes and can cause cell death by permanently disruption translation. In addition to the inhibition of protein synthesis, these toxins have been reported to influence a diverse set of biochemical processes in the eukaryotic cell. However, the molecular mechanisms that control sensitivity of wheat and barley to trichothecenes are not well understood. Cellular factors that influence how the toxins are taken up, processed, and transported before inhibiting translation have not been identified. The goal of our research is to develop a better understanding of the genetic basis of eukaryotic cell susceptibility to trichothecene mycotoxins. Yeast, Saccharomyces cerevisiae, is sensitive to a wide variety of trichothecene mycotoxins and thus provides an ideal model organism to identify the cellular targets of these toxins. The availability of several complete sets of deletion libraries provides a powerful approach to identify genes critical for conferring sensitivity to trichothecenes on a genome-wide scale. We have carried out a genome-wide screen of the non-essential yeast knockout library (YKLO) to identify the genes that confer resistance to trichothecenes when deleted. We screened 4720 homozygous diploid YKO strains and identified 122 strains that showed resistance to 4 micromolar trichothecin (T-cin), 27 of these strains also showed resistance to 6 micromolar T-cin and 14 strains showed resistance to 8 micromolar T-cin. The broad categories of genes identified in resistance screen include genes that influence translation, trafficking, signal transduction, protein folding/degradation, biosynthesis/metabolism, the cell cycle, membranes, gene regulation, and mitochondria. The majority of identified genes were associated with mitochondria, implicating mitochondria in the toxin mechanism of action. These genes represent potential targets for engineering resistance to Fusarium head light (FHB) and for developing effective approaches to prevent mycotoxin contamination of cereals.